Excessive foaming is often a result of a buildup of body oils, cosmetics and soap residue left in bathing suits. Just remove foam with a skimmer net and rinse your filter(s). You may have to do this several times.  Very small amounts of ‘Dirty Foam’ at times may appear. This is simply the Natural Hot Tub Company Water Treatment & Conditioner taking contaminants to your filter(s).  To prevent foaming, double rinse bathing suits in hot water to remove dyes, soap and phosphates found in detergents.  A less likely cause of excessive foam is due to soft water under 100ppm.  A calcium increaser may be needed to solve this issue.